Well, I just went through all my old PATA drives looking for the MySQL dump from an earlier incarnation of this blog, and it appears that the data is well and truly gone forever. I made a backup image of a candidate drive, which was very lucky: the heads crashed hard whilst I was running TestDisk on it.
But I’m not really able to make sense of the image anyway. It looks like this IBM drive is from my original OS X/Mac OS box that I bought nearly 15 years ago. At some point I put it in a FireWire (remember that?) enclosure as a bootable Mac OS drive (when Apple still supported that) so I could play Alpha Centauri, and from there it ended up as an OpenBSD backup drive. So, most partition-level tools see a complete mess of HFS and DOS partitions containing a hodge-podge of duplicate HFS+, NTFS, and FFS filesystems.
It’s an intractible mess, or at least enough of a mess the rewards are not worth the effort. Just use the Internet Wayback Machine if you want to see how much I used to swear on my blog. (Hint: a lot.)
I suppose I did become an instant expert in Linux partition and filesystem tools. I still think the best solution to data loss is to not make data you are afraid to lose.